λ/4-filters are used, for example, in high frequency technology as bandpass filters. Such filters have, for example, a short-circuit line of fixed length between a signal-conducting conductor and a ground. The bandwidth of the filter depends on the length of the short-circuit conductor, which determines the center frequency of the filter according to the equation f0=c/λ. The bandpass character of such a filter is obtained from the special wave characteristic at high frequencies, since, at high frequencies, the short-circuit at the center frequency f0 is blocked, so that signals with frequencies that are distributed over a certain bandwidth about the center frequency can pass through the conductor.
Such filters are also used for surge protection, for example, in mobile telephony.
Thus, for example in DE 9422 171 U1 describes a surge voltage protection plug connector for a coaxial cable having an inner and an outer conductor, where a spiral-shaped short-circuiting stub of fixed length short circuits the inner conductor with the outer conductor.
From U.S. Pat. No. 6,061,223, for example, a surge voltage protection device is known, in which an inner conductor is arranged in a housing, which together form a coaxial line. A spiral-shaped conductor of fixed length is used as a short-circuit element to transfer the energy during a surge voltage event to a ground connection.
One drawback of the mentioned filter is that, due to the fixed short-circuit length, the center frequency is determined in a fixed way. A different filter therefore must be used for each different frequency behavior.